Norovirus in a Dutch tertiary care hospital (2002-2007): frequent nosocomial transmission and dominance of Glib strains in young children

We report a retrospective analysis of norovirus (NoV) infections occurring in patients of a tertiary care hospital during five winter seasons (2002/03 to 2006/07). Data were compared with national surveillance data and with corresponding data for rotavirus. Between July 2002 and June 2007, faecal. specimens from 221 (9.0%) of 2458 hospital patients with diarrhoea tested positive for NoV. The incidence in children varied from 2.52 per 1000 admissions in 2004/05 (when testing began to be performed routinely) to 11.9 per 1000 admissions in 2006/07, white the incidence in adults remained stable (mean: 1.49 per 1000 admissions). Two genotypes predominated during the study period: Glib strains occurred mainly in children below the age of two-and-a-half years [odds ratio (OR): 14.7; P < 0.0001] whereas GII.4 strains affected all age groups. Compared with rotavirus infections, NoV infections in children were more often hospital-acquired (59% vs 39%, OR: 2.29; P < 0.01). Among these cases we identified 22 clusters of NoV infection among inpatients. Twelve of 53 patients from whom follow-up samples were available demonstrated tong-term virus shedding. We report a dynamic pattern of sporadic NoV infections in large hospitals, with frequent nosocomial, transmission and with the predominance of GIIb-related strains in children. Effective prevention strategies are required to reduce the impact of sporadic NoV infection in vulnerable patients. (C) 2008 The Hospital Infection Society. Published by Elsevier Ltd. All rights reserved.